Have you tried gas drops? I gave them to my dd before and after each feed when she was bf, and now since she's been on bottles I put a drop in the bottle.
As for changing her routine...My dd took 30 min. naps for the 1st 6 mos of life. Even if she did this 5 times a day, her bedtime and wake up time we the same (8-8). Therefore, even though she's going to be cranky until she adjusts, you'll just have to bite the bullet and give it a try. Do your best to extend her naps. But like you said, if you can't, you'll just have more A time before the next feeding. Then, if she's had a short nap, really watch her sleep cues and get her down for the next nap so that she won't be overtired. Again, do your best to extend them if possible. If you keep a consistent 3 hr feed schedule, I truly think you'll see things fall into place, and at least this way you'll have something to count on. Then, when she goes down at 5:30, if this is her best nap, get her up in 1-1.5 hrs. Try to keep her calm with some low key activity, bath, stories, then feed around 7, and in bed by 7:30. Then, you can do the df at 10, and see where that gets you. But, she is probably going to keep waking for the day at 5 am if she's going to bed at 5:30 pm. IF you don't want to do it all at once, cut back on her sleep after 5:30 by 30 min increments. For example, if she usually wakes at 9:30, wake her at 9, then the next day or two, at 8:30. Also, the more feeds you can get into her between 7am and 10 pm (with the df), the quicker I think she'll drop the middle of the night feeds unless they become habitual, then that's another situation to work through. Does any of this help?